The present invention relates to an electrosurgical system, and in particular to an electrosurgical system which is used in a n environment where fluid is present during use.
Electrosurgery typically involves the use of radio frequency (RF) alternating currents to modify body tissue. Usually during electrosurgery the RF currents are passed through tissue at a treatment site, either killing the tissue and at the same time causing it to dissociate into tiny fragments (known in the art as vaporisation), or creating substantial heat at or nearby the treatment site to coagulate proteins from which tissue is made, and possibly also subsequently to desiccate the tissue. Vaporisation is a technique used either to cut tissue, in which case a relatively small channel of tissue separating two tissue masses is vaporised to enable parting of the tissue masses, or to ablate tissue, a process in which relatively large volumes of tissue at a treatment site are vaporised, which may for example result in the creation of a crater in the tissue. A coagulation procedure is typically performed to staunch the flow of blood from bleeding tissue, while depending upon the temperature to which the tissue at the treatment site is raised during coagulation, a desiccation procedure may follow inevitably subsequent to the coagulation, and involves heating the tissue to a point where moisture is driven out of the tissue, causing it to shrink as a result.
The application of electrosurgical techniques has advantages over traditional forms of surgery, in that, by using electrosurgery, a larger range of procedures may be performed using minimally-invasive surgical techniques. In addition, the ability to coagulate subsequent to, for example, the removal of a tissue mass reduces post-operative bleeding and results in shorter healing times.
Traditionally there are two forms of electrosurgery. Monopolar electrosurgery involves the delivery of RF power to a treatment site from an electrode on an electrosurgical instrument which is manipulated by a surgeon during the surgical procedure. Alternating current supplied from an electrosurgical generator flows through the patient""s body between the electrode on the instrument and a further electrode, which is usually an electrically-conductive plate located in contact with the outside of the patient""s body. Because the current density is only relatively high in the immediate vicinity of the electrode on the instrument, the passage of current through the patient""s body to the external plate does not cause the modification of tissue in regions remote from the electrode on the instrument, and therefore the treatment site. Thus, it is only the electrode on the instrument which may said to be xe2x80x9cactivexe2x80x9d, i.e. modifies tissue.
In a bipolar system, the instrument has two or more electrodes, and current passes between the electrodes in a region local to the treatment site. In one form of bipolar electrosurgical system, unwanted tissue damage is avoided by constructing a bipolar instrument with an active or tissue treatment electrode, and a xe2x80x9creturnxe2x80x9d electrode. The active electrode has a substantially smaller surface area than the return electrode, as a consequence of which the current density in the region of the active electrode is correspondingly higher than in the region of the return electrode. Since the magnitude of the current density determines whether tissue modification takes place, tissue in the region of the active electrode will experience modification as a result of the passage of current between the electrodes, whereas tissue in the region of the return electrode will not.
Both monopolar and bipolar electrosurgery are frequently performed in the presence of a liquid supplied to the treatment site. The liquid may be non-conductive, such as distilled water, glycine or sorbitol, in which case current passes between the electrodes only via tissue, meaning that, under normal conditions, both electrodes must be in contact with the tissue to enable current to flow. Alternatively, the liquid may be conductive, such as normal saline, in which case any conduction path between the electrodes will most likely include the liquid. In each case, the performance of electrosurgical procedures in the presence of a liquid can result firstly in the presence of tissue debris floating within the liquid, and secondly of bubbles within the liquid, both of which may obscure the surgeon""s view of the treatment site (which, since the surgery is likely to be minimally invasive will most likely be provided by means of a remote viewing device, such as an endoscope or some other form of fibre-optic link).
A bipolar electrosurgical instrument is known from International Patent Application WO 97/00646 having a coaxial supply channel by means of which electrically-conductive fluid may be supplied to the treatment site, and a central return channel by means of which fluid and tissue debris may be removed from the treatment site. In use, saline fluid is fed down the supply channel under gravity, and removed along the return channel under suction.
The present invention provides an alternative to the prior art instrument, which inter alia enables existing instruments to be employed in operative environments where it is desirable to provide suction in the region of the treatment site.
A first aspect of the present invention provides an electrosurgical system comprising an electrosurgical instrument having a handle defining a proximal end of the instrument and by means of which the instrument may be manipulated by a user; a shaft extending from the handle; and an active tissue treatment electrode on the shaft which is axially spaced from the handle and which defines a distal end of the instrument; the system further comprising an elongate removable sheath adapted to extend coaxially with, and externally around, the shaft of the instrument, the sheath comprising an outlet port, an opening on the distal side of the outlet port, and sealing means on the proximal side of the outlet port for forming a substantially fluid-tight seal with the instrument, thereby to enable low pressure applied at the outlet port to be transmitted to the opening to create suction in the region of the opening.
The sheath may be optionally employed as desired depending upon whether removal of fluid and/or debris from the treatment site is desirable during the procedure to be performed. For example, it may be desirable to omit the sheath if a coagulation or a desiccation operation is to be performed, but to employ the sheath during vaporisation where significant amounts of bubbles and/or debris are created.
In a preferred embodiment, the sealing means cooperates with the shaft of the instrument to form the fluid-tight seal. In an alternative embodiment, however, a seal may be formed between cooperating surfaces provided by, for example, a part of the handle and an appropriately configured surface at the proximal end of the sheath.
In certain electrosurgical systems, and in particular in systems which are designed to operate in the presence of electrically-conductive fluid, the power applied to the instrument in order to achieve vaporisation requires very precise control, and is critically dependent upon the formation of a vapour pocket around the active electrode. In such systems, the sucking of fluid and/or debris away from the treatment site may have the effect of causing the flow of fluid over the active electrode as a result of the applied suction to remove heat so rapidly as to quench the vapour pocket, thereby rendering the instrument incapable of vaporisation while suction is applied. Preferably, therefore, in circumstances where the instrument and sheath are to be used for vaporisation, means will be provided for locating the opening on the sheath at a predetermined distance away from the active electrode. For a given flow rate at the outlet port of the sheath and power dissipation at the active electrode, the opening in the sheath may thus be positioned sufficiently far from the active electrode to prevent quenching of the vapour pocket, and yet sufficiently close to provide the requisite suction for the removal of liquid and/or debris. In one embodiment, the opening in the sheath is located by means of an abutment between two mutually-engageable surfaces on the sheath and the instrument. Preferably, the abutment will be between the handle of the instrument and an abutment surface in the region of the proximal end of the sheath.
In a preferred embodiment, the internal diameter of the sheath is larger towards the proximal end in the region of the outlet port than it is at the distal end in the region of the opening. This has a number of advantages. Firstly, it enables a relatively low flow rate applied by, for example, a vacuum pump connected to the outlet port to be translated into a substantial pressure drop at the opening; the low flow rate means that the opening may be positioned relatively close to the active electrode without quenching any vapour pocket which may be present, while the resultant high pressure drop provides powerful suction in the region of the treatment site. Secondly, in the event that blockage occurs in the lumen between the electrode shaft and the sheath, the instrument may be retracted within the sheath until the clearance between the instrument shaft and the sheath becomes sufficiently large (as a result of the greater internal diameter of the sheath towards the proximal end thereof) to enable the material causing the blockage to pass between the shaft and the sheath under the action of the suction applied at the outlet port.
In a preferred embodiment, the sheath is translucent, to enable easy visualisation of the passage of bubbles and/or debris from the treatment site. This enables a user to determine if the sheath is blocked, whereupon retraction of the sheath as described above may be performed to enable the blockage to be cleared.
In yet a further embodiment, the sheath is made of a relatively flexible material. This avoids limiting the range of procedures for which the instrument may be employed as a result of its size; if the sheath is flexible, then it is capable of deforming when the shaft of the instrument is inserted into relatively confined spaces.
All aspects of the electrosurgical system and elements thereof described and illustrated herein are equally applicable to monopolar and bipolar electrosurgical systems.
Yet a further independent aspect of the present invention provides a method of operating an electrosurgical system comprising an electrosurgical instrument having a handle at a proximal end thereof by means of which the instrument may be manipulated, a shaft extending from the handle on which an active tissue treatment electrode is located at a distal end of the instrument, and an electrosurgical generator connected to the active electrode to supply radio frequency power thereto, the method comprising the steps of:
sheathing at least a part of the shaft of the instrument in a substantially fluid-tight chamber, the chamber having an opening located in the vicinity of the active electrode;
immersing the active electrode within a liquid;
operating the generator to apply radio frequency power to the active electrode; and
reducing pressure within the chamber, thereby creating suction at the opening in the region of the active electrode.
Typically, the method will be performed using a bipolar instrument which additionally has a return electrode located on the shaft, with both the active and return electrodes being immersed in an electrically-conductive fluid which completes the conduction path between the electrodes. In one embodiment of the method, the generator is operated to apply power to the active electrode to cause it to operate in vaporisation mode whereby a vapour pocket is created around the active electrode, and the suction at the opening of the chamber does not create a sufficient flow of liquid over the active electrode to quench the vapour pocket.
Although the use of a sheath as described herein may be employed to remove bubbles and/or tissue debris from a treatment site, it may equally be employed for other purposes such as the supply of fluid to a treatment site, or to provide suction for a purpose other than removal of bubbles and/or tissue debris.